1. Technical Field
This invention relates to a multistage depressed collector (MSDC) klystron based amplifier, and more particularly to an MSDC klystron for use in ground based satellite and terrestrial communications.
2. Description of Background Art
Klystron tubes are known devices used for high power transmission of microwave signals. Klystrons are used typically in terrestrial transmission of radio frequency signals, such as for VHF or UHF transmission of radio and television signals. Klystrons also have use in uplink paths in ground to orbiting satellite systems.
There is a continuing effort to make klystron tubes more efficient as well as smaller with the same or increased output power. Heat loss, as well as power loss due to inefficient tube operation, is under continuous scrutiny. Multistage depressed collector tubes have been discussed in the prior art. U.S. Pat. No. 4,395,656, issued Jul. 26, 1983, is entitled Gyrotron Transmitting Tube. This patent discloses an R.F. transmitting tube and a multistage depressed collector to capture spent, spinning or orbiting electrons from a magnetic focusing area. It is the resonance due to the electrons in the magnetic field that determines the frequency of the output of the gyrotron tube. Marrying the MSDC technology in a high power uplink klystron tube suitable for satellite and terrestrial communications above 1 GHz, however, has been an unreached goal.
The present invention relates to a high-power output vacuum electron device for use in a ground based satellite or terrestrial communications system. The invention includes a cathode for emitting a supply of electrons and an anode for attracting electrons, with the anode being constructed to allow electrons to pass through the anode. An RF generator circuit in the path of the electron beam generates RF signal energy in the presence of the high-voltage power source. A magnet surrounds the anode and the RF generation circuit for focusing the electrons into a collimated beam. A collector receives a collimated electron beam and returns the collected electrons to the cathode. The collector is a multistage depressed collector and the vacuum electron device is a klystron. Another embodiment of the invention includes the ground based satellite or terrestrial communications system with a klystron in with a multistage depressed collector, and further including a power supply for supplying power to the klystron, and a control system for controlling the operation of said ground based satellite or terrestrial communications system, power supply, and klystron. A predistortion linearizer may be used for linearizing the output of the klystron. The system also may include a block upconverter for accepting radio frequency input at an intermediate frequency and of converting the intermediate frequency to the microwave frequency for amplification by the klystron. An electronic control for the beam voltage to the klystron is also included for allowing beam voltages lower than nominal to decrease power consumption when the klystron is not at full output power.